Contamination is a rare Enchantment card from Mystery Booster 2 (MB2), collector number 178. Current market price: $4.97 (foil $35.99), TCGplayer market prices via Scryfall.
At the beginning of your upkeep, sacrifice this enchantment unless you sacrifice a creature. If a land is tapped for mana, it produces {B} instead of any other type and amount.